1. Field Of The Invention
The present invention relates to improvements in the cement-concrete structures in general and, to the following in particular:
1) General purpose concrete (up to 3000 psi) PA0 2) Exterior-interior cement board, and PA0 3) Mortar, all of which provides resistance to cracking, improves shock wave absorption, lowers heat conductivity, and reduces noise levels simultaneously.
2. General Background
Conventional concrete is a mixture of cement (Ca, Si, Al, Fe, Mg, Na and K), sand, aggregate and water. It has been found that cements containing 1% or more of sodium oxide and potassium oxide will react with aggregates containing opaline silica, highly siliceous rocks and limestone, The formation of the new compounds causes the interior of the concrete to expand, resulting in surface cracking, which for years has been accepted as natural to its use.
Reinforced (steel) concrete was invented by Thaddeus Hatt in 1878, U.S. Pat. No. 206,112 and over the years many improvements have been made in the use of inorganic fibers and others, such as alumina, asbestos, glass, graphite, etc.; the features of which are disclosed, for example, in U.S. Pat. Nos. 3,992,172; 4,316,925 and 4,337,094.
SUMMARY OF THE PRESENT INVENTION
While the above and other improvements no doubt represent advances in the cement concrete structures, they do nothing in the areas of crack resistance, shock wave absorption, heat conductivity reduction, and noise level reduction.
Accordingly, it is an object of the present invention to provide rubber crumb reinforced cement-concrete structures that will implement the above mentioned improvements.
In accordance with this invention, these and other objects and advantages are achieved by dispersing said rubber crumbs (natural and synthetic) in the structures, from about 1% to about 30% by weight of the cement, based on product application.